使用此代码:
public class App extends Application {
private static App instance;
@Override
public void onCreate() {
super.onCreate();
initRealmDB();
}
private void initRealmDB() {
instance = this;
Realm.init(this);
RealmConfiguration realmConfiguration = new RealmConfiguration.Builder().modules(new SimpleRealmModule()).name("RealmSample.realm").build();
Realm realm = null;
try {
realm = Realm.getInstance(realmConfiguration);
realm.setDefaultConfiguration(realmConfiguration);
} finally {
if (realm != null) {
realm.close();
}
}
}
}
**In use:**
Realm realm = Realm.getDefaultInstance();
RealmResults<OrganizationModelClass> results = realm.where(OrganizationModelClass.class).findAll();
if(realm.isInTransaction())
{
realm.cancelTransaction();
}
realm.beginTransaction();
if (results != null) {
if(membershipList != null)
{
membershipList.clear();
}
for (int i = 0; i < results.size(); i++) {
Log.d(OrganizationActivity.class.getName(), " i :" + results.get(i).getCurrent_membership_uuid());
}
}
这是最好的使用方式吗?我应该使用单身方法吗?如果还有其他好的方法来完成这项任务,请与我分享。我遵循这个https://dzone.com/articles/realm-practical-use-in-android但这段代码不能使用这种依赖:classpath“io.realm:realm-gradle-plugin:3.3.1”
Realm realm = Realm.getInstance(SimpleRealmApp.getInstance());
这是最好的使用方式吗?
没有
Realm realm = Realm.getDefaultInstance(); // <-- opens Realm
RealmResults<OrganizationModelClass> results = realm.where(OrganizationModelClass.class).findAll();
if(realm.isInTransaction())
{
realm.cancelTransaction(); // <-- what if that transaction was important?
}
realm.beginTransaction();
if (results != null) {
if(membershipList != null)
{
membershipList.clear(); // <-- ??
}
for (int i = 0; i < results.size(); i++) {
Log.d(OrganizationActivity.class.getName(), " i :" + results.get(i).getCurrent_membership_uuid()); // <-- if the result set was modified here because of the transaction, then the RealmResults will update, and you'll skip elements
}
// <-- where is the commit?
} // <-- where is realm.close()?
代替
try(Realm r = Realm.getDefaultInstance()) {
r.executeTransaction((realm) -> { // AS 3.0+ desugar
RealmResults<OrganizationModelClass> results = realm.where(OrganizationModelClass.class).findAll(); // <-- get in transaction
for (OrganizationModelClass model : results) { // uses snapshot() internally
Log.i(model.getClass().getName(), getCurrentMembershipUuid());
}
}
} // <-- auto-close because of try-with-resources
我应该使用单身方法吗?
使用getInstance()
/ getDefaultInstance()
打开的领域实例是线程本地和引用计数,因此它不适合在整个应用程序中用作单例。您需要打开线程本地实例。
所以在UI Thread上,基于documentation:
// Setup Realm in your Application
public class MyApplication extends Application {
@Override
public void onCreate() {
super.onCreate();
Realm.init(this);
RealmConfiguration realmConfiguration = new RealmConfiguration.Builder()
//.deleteIfMigrationNeeded()
.migration(new MyMigration())
.build();
Realm.setDefaultConfiguration(realmConfiguration);
}
}
// onCreate()/onDestroy() overlap when switching between activities.
// Activity2.onCreate() will be called before Activity1.onDestroy()
// so the call to getDefaultInstance in Activity2 will be fast.
public class MyActivity extends Activity {
private Realm realm;
private RecyclerView recyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
realm = Realm.getDefaultInstance();
setContentView(R.layout.activity_main);
recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
recyclerView.setAdapter(
new MyRecyclerViewAdapter(this, realm.where(MyModel.class).findAllSortedAsync(MyModelFields.ID)));
// ...
}
@Override
protected void onDestroy() {
super.onDestroy();
realm.close();
}
}
// Use onCreateView()/onDestroyView() for Fragments.
// Note that if the db is large, getting the Realm instance may, briefly, block rendering.
// In that case it may be preferable to manage the Realm instance and RecyclerView from
// onStart/onStop instead. Returning a view, immediately, from onCreateView allows the
// fragment frame to be rendered while the instance is initialized and the view loaded.
public class MyFragment extends Fragment {
private Realm realm;
private RecyclerView recyclerView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
realm = Realm.getDefaultInstance();
View root = inflater.inflate(R.layout.fragment_view, container, false);
recyclerView = (RecyclerView) root.findViewById(R.id.recycler_view);
recyclerView.setAdapter(
new MyRecyclerViewAdapter(getActivity(), realm.where(MyModel.class).findAllSortedAsync(MyModelFields.ID)));
// ...
return root;
}
@Override
public void onDestroyView() {
super.onDestroyView();
realm.close();
}
}
有关后台线程,请参阅docs:
Thread thread = new Thread(new Runnable() {
@Override
public void run() {
try (Realm realm = Realm.getDefaultInstance()) {
// No need to close the Realm instance manually
}
}
});
thread.start();
如果你想使用Realm作为单例,你必须使用一个可以递增,递减和获取实例的类,而不增加线程本地领域的引用计数,有点像this experiment here。
public RealmController(Context context) {
realm = Realm.getDefaultInstance();
}
public static RealmController with(Activity activity) {
if (instance == null) {
instance = new RealmController(activity.getApplication());
}
return instance;
}
public static RealmController with(Application application) {
if (instance == null) {
instance = new RealmController(application);
}
return instance;
}
public static RealmController getInstance() {
if (instance == null) {
instance = new RealmController(SysApplication.getAppContext());
}
return instance;
}